1. Field of the Invention
This invention relates to materials for repairing pavement surfaces and methods for their repair. In particular, it relates to naturally occurring bituminous sandstone material and its use in "cold patch" repair of pavement surfaces.
2. Discussion of the Prior Art
Pavement surfaces, by their very nature, are subject to continuous wear by their users, i.e. by the constant travel of pedestrians, automobiles, and aircraft. Pavement surfaces are also subject to degradation, because they are exposed to the elements, i.e. rain, snow and extreme temperatures. As a result, pavement surfaces are repeatedly damaged by the formation of cracks, potholes, and the like. Consequently, there is a great need for materials which can be simply and inexpensively used to repair such damage to pavement surfaces.
One method for repairing pavement surfaces is known as "hot patch" repair. Hot patch repair employs a tar-like material which is heated to approximately 400.degree. F. and then immediately forced into damaged areas. A major drawback of hot patch materials and methods is that they require relatively expensive equipment to heat the tar-like material on-site. Further, the method generally requires that the damaged pavement be pre-treated with a preliminary coating of a base material to provide sufficient bonding between the material and the damaged area.
Another method of repair is described in U.S. Pat. No. 4,859,502, which patent is herein incorporated by reference. The method employs mixing bituminous sandstone with 20 to 56% water by weight, to form a slurry having a temperature of from 110.degree.-210.degree. F. The slurry is then pumped through a conduit and applied to the area to be repaired. Among the disadvantages of the method disclosed in this patent is the cost of the equipment needed to form the hot slurry and then pump the hot material to the damaged area.
Attempts have also been made to use bituminous sandstone, in cold patch repair--i.e., without heating. In central Utah, where large deposits of bituminous sandstone exist, roads are initially constructing using this material. When road damage occurs additional bituminous sandstone is used to repair the holes without special processing or treatment. Unfortunately, the naturally occurring material is difficult to work with, because it is typically mined in aggregate chunks which are difficult to reduce to a uniform grain size. Accordingly, the untreated material is not effective in filling cracks and other damaged areas, where the consistency of the bituminous sandstone is of importance.